1. Field of the Invention
The present invention relates generally to machining devices and, more particularly, to a rotary machining device for machining a flat surface on a workpiece.
2. Description of the Prior Art
There are many different types of manufacturing applications in which it is desirable to machine a flat surface on a workpiece. For example, one such application would be to machine a flat surface for the cylinder head on a cylinder block for an internal combustion engine. In such applications, it is desirable and oftentimes necessary that the machine surface be as flat as possible so that the engine block and the cylinder head mate together.
When machining such workpiece surfaces, it has been the previous practice to utilize a linear ram. In a linear ram, the ram is mounted on an elongated track and includes a plurality of broaching tools mounted to its lower surface. With the ram positioned at one end of the track, the workpiece is secured to the track so that its surface to be machined faces upwardly and in alignment with the lower surface of the ram. Thereafter, the ram is propelled along the track to the opposite end by hydraulic or other suitable means and, in doing so, machines the desired surface of the workpiece. The ram is then retracted to the first end of the track and the process is repeated.
The previously known linear rams, however, are disadvantageous for a number of different reasons. One disadvantage of the linear ram is that the ram must be propelled along the track, stopped at the opposite end of the track and retracted for each machining operation. Thus, due to the cyclic operation of the ram, the power requirements for the linear ram are excessive when compared to the actual machining performed.
A still further disadvantage of many linear rams is that the machine cycle time is necessarily long, typically in excess of 25 seconds, due to the required stopping and retraction of the linear ram for each machining cycle. Moreover, since the ram must attain a predetermined speed from a dead stop before the machining of the workpiece commences, the ram with its associated track is bulky in construction and occupies a great deal of space.
A still further disadvantage of these previously known rams is their massive size requirements and the limitation of the cutting speed due to their size limitations and required cycling. The relatively low cutting speed and single pass operation of these rams causes excessive cutting tool pressure on the workpiece which can damage fragile and/or thin workpieces. Lastly, these linear rams are capable of machining only a single workpiece per machining cycle.
There have, however, been a number of previously known rotary broaches or cutting machines, such as that disclosed in U.S. Pat. No. 2,113,554 to J. R. Johnson. This rotary broach, however, was disadvantageous for a number of reasons. First, the wheel containing the cutting tools was cyclically rotated and stopped for each machine cycle. Because of this, only low speed machining of the workpiece was obtainable. Moreover, only a single workpiece could be machined at a given time and at a given work station.